The present invention relates to a clamp for holding a stage-mounted device relative to a stage support truss. More specifically, the present invention defines a hook clamp which holds the weight and position of the stage-mounted device while it is being mounted to the support truss, and also has an electrical connector extending through the clamp.
Many stage-mounted devices require a stable base of support. Moving stage lights are often particularly sensitive to such requirements. Typically, moving lights are electronically controllable to move between various positions and to provide special effects. The position of a moving light, however, is accurate only when the system has a very stable base of support. Moreover, because of the lamp size, cooling requirements, and complicated electronics, these lamp devices can be very heavy. Many times such lights are mounted at the upper area of the stage, very high off the ground.
Many lamp clamps are known in the art. Some of the commonly used ones are described herein. A Cheeseborough clamp (U.S. terminology) or Scaff clamp (U.K. terminology) is shown in FIG. 1. The clamp 100 is shown in its open position in FIG. 1. The moving part 122 of the clamp.pivots around pivot point 104 to form a closed clamp as shown in FIG. 2 which closes around the supporting pole or pipe. The clamp can be tightened by tightening bolt 106 relative to bolt accepting mechanism 108, which can be a slot or the like in a plate. The appropriate tightening reduces the size of the inner surfaces, to tighten the clamp and to maintain the lamp in position relative to pole 200.
The inventors of the present invention recognized that this system is very difficult for the installers to use. One main reason is because the entire weight of the lamp must be supported by the installer while attaching the lamp to the pole 200. FIGS. 1 and 2 show these clamps in the open and closed position, respectively to demonstrate the installation. In order to install the lamp, the installer must hold lamp 110 while placing the open clamp 100 against pole 200 and while holding surface 120 of the open clamp against the supporting pole 200. The clamp is hinged around pivot 104 to form a cylindrical inner area 205, as shown in FIG. 2. Bolt 106 holds relative to bolt accepting element 108.
In order for the lamp to be properly attached to the supporting pole 200, therefore, the bolt 106 must be screwed into the accepting element 108 (e.g., a nut or a split holder). Alternately, a wing nut or like mechanism on element 108 can be screwed into bolt 106. In any of those cases, the installer must hold the weight of the lamp, which can be as heavy as 60 pounds, while holding the clamp closed and simultaneously screwing the nut into place. Moreover, even once the nut is screwed into place, the lamp is still not maintained in its proper position relative to the pole until the nut and screw 106, 108 are properly tightened.
These most-common kind of-lamp clamps have been recognized by the inventors of the present invention to cause problems, making the lamps very difficult to install.
A second kind of mounting mechanism is shown in FIG. 3. The lamp 110 is connected to a folded piece of metal 300 which includes vertically extending portions 302 and 304, and a horizontal portion 306. The inside surface 308 of clamp 300 is placed against the supporting pipe 200. Since the metal 300 is formed of folded flattened metal sheets, the inside surface 308 touches the pole 200 only at tangent points between the flat surfaces and the round pipe, such as 310. Rotation of lamp 110 relative to pole 200 is prevented by tightening set screw 312 against point of contact 314 on the pole 200.
There are still problems with this system. Significantly, this system allows the weight of the lamp to be placed on the pole prior to tightening the set screw 312. However, the lamp can still rotate relative to the pole, at least until the set screw is tightened against the pole. Moreover, this design tends to distort the roundness of the pole because of the large amount of force at the location 314 where the set screw 312 touches the pole. As can easily be seen, moreover, the system is inherently unbalanced.
A different, but similar kind of prior art clamp is shown in FIG. 3A. That clamp includes the same basic structure as shown in FIG. 3. It includes the set screw 312 which presses against a portion of the support pole 200. Ridges 350 and 352 provide extra friction to hold the lamp relative to the pole.
Power must also be applied to the lamp. Typically the power travels either along the pole or along a separate conduit which is near the pole. The inventors of the present invention have recognized the inconveniences and difficulties which often occur in getting the power to the lamp.
Since the lamps are very heavy, it is also important to ensure that the lamp does not fall from its position on the pole. Accidents can happen, for example, if a technician fails to properly secure the lamp to the pole, or if the securing mechanism fails. Such accidents risk both damage to very expensive equipment, as well as a serious threat to stage workers. One aspect of the present invention proposed a fail-safe mechanism for a lamp.
It is also desirable that the lamp mounting mechanism be versatile in its selection of mounting techniques. One particularly interesting mounting technique is a floor mounting. This technique uses a plate or other support base holding special flanges on the clamp. Those flanges position the lamp and clamp xe2x80x9cupside downxe2x80x9d relative to the position in which the lamp would be if pole mounted.
It is an object of the present invention to provide a clamp which allows flexibility and safety by special techniques which can be used individually or in combination. This is done according to the present invention by providing an element which has interior surfaces defining an area which approximates in shape the outer surface of the supporting truss, over at least over half of the outer surface of the truss support. This ensures maximal frictional contact between the support and the clamp. This friction maintains the lamp in its proper position relative to the truss, even prior to frictional tightening.
A movable element tightens a tightening device into contact with the support element to further maintain the lamp in position. The inventor recognized that the combination of an inner surface approximating the outer surface of the support pole, and a design that allows hooking over the support pole produces a much easier-to-use system.
Structure is provided in the clamp that facilitates the channelling of power to the lamp. One aspect of this invention includes a special structure incorporated within the clamp which facilitates power routing to the lamp. This structure includes surfaces defining a special hole in a special location on the clamp. A special connector receives power and routes the power to a power conduit. That power conduit is routed around the rear of the connector through another hole and into the lamp. This aspect facilitates application of power to the lamp without the need to provide a separate external power conduit.
Another feature of the present invention uses a fail-safe mechanism which allows a safety cable through the clamp and around the pole. A technician mounting the lamp can initially connect the safety cable to avoid the lamp falling or the like while it is being installed.
Another feature of the present clamp provides two separate mounting surfaces: a first surface which allows connection to a support pole such that the clamp is secured in a first orientation, and a second surface which allows connection in a way such that the clamp is secured in a second orientation, different than the first orientation. The preferred surfaces include pole mounting surface, mounting the lamp on the bottom of the clamp, and a floor mounting surface mounting the lamp on the top of the clamp.